The invention relates to triggering an intelligent network service controlling a basic call state model at a switching point and especially in a situation where an intelligent network service has already been triggered before said triggering.
In telecommunications networks, intelligence refers to the ability to access stored data, to process the data and to make decisions based on the data. Even the present telecommunications networks, such as the public switched telephone networks PSTN, are to some extent intelligent, since they are capable of processing stored data in routing a call, for instance. A typical xe2x80x98intelligentxe2x80x99 facility in present telecommunications networks is conditional call forwarding in which the call situation must be analysed and the call routed on according to the stored call forwarding service profile. Intelligent facilities of this kind have, however, so far been an inseparable part of the basic network and consequently, changing or adding facilities has required software updating, for instance, in all network switching centres.
An intelligent network IN is a network architecture attached to a basic network (fixed or mobile network, for example), which enables a swifter, easier and more flexible implementation and control of services. This is done by moving the control of the services away from the switching centre to a separate intelligent network functional unit which in the following will be called a service control point SCP. This way, the services can be made independent of the operation of the basic network, and the structure and software of the basic network need not be altered when services are changed or added. The network elements which manage the intelligent network interface are called service switching points SSP. An SSP is typically a network element responsible for connection set-up, e.g. a switching centre of the basic network.
A control record of a call is, in general, modelled with an incoming side call model and a terminating side call model at the switching point SSP. The incoming side call control is related to the services of the caller, i.e. A subscriber, and the terminating side call control is related to the services of the receiver of the call, i.e. B subscriber. The reason why the call must be modelled is that to be able to control call set-up at the SSP, the SCP must know the phase of the call. By means of modelling, both the SSP and the SCP know implicitly the detection points DP, i.e. the call phases and possible interaction points, at which the SCP may influence the call. A detection point is either a trigger detection point TDP or an event detection point EDP. There are two EDP and TDP types: R, i.e. xe2x80x98Requestxe2x80x99, and N, i.e. xe2x80x98Notificationxe2x80x99. When the SSP makes an SCP enquiry at a detection point DP of type xe2x80x98Requestxe2x80x99, call processing must be interrupted until a response is received from the SCP. With the xe2x80x98Notificationxe2x80x99 type, the SSP only sends a notification at the detection point and does not interrupt call processing or wait for a response. The TDP detection points are statically defined at the SSP and they detect the event or trigger which triggers an intelligent network service when certain conditions are met. An intelligent network service is triggered by sending a start message leading to the initiation of the service to the service control point. In response to the message, the service control point initiates a service logic, on the basis of which the SCP sends to the SSP an instruction on event detection points EDP to be reported, for instance. After receiving the instruction, the SSP arms the detection points to be reported. If the detection point of the trigger is a request-type TDP-R, a connection controlling the state model is set up and exists as long as there is an active request-type event detection point EDP-R armed by the SCP.
In present intelligent networks, only one controlling connection can be set up in one call state model. The situation is, however, about to change as the standardization of intelligent networks progresses. According to plans, it will be possible to have, in one call state model, several controlling connections (MPC, multiple point of control support) to one or more service control points in an intelligent network according to the ETSI (European Telecommunication Standard Institute) SPS3 work group and the CoreINAP (intelligent network application protocol) CS3 (capability set 3) being developed by ITU. In other words, more than one intelligent network services can provide instructions to the same call state model at an SSP. The services controlling the same state model are, however, independent of each other, and do not necessarily have any knowledge of each other. Here, the problem is that there is no mechanism to take care of the interoperability of the facilities of parallel controlling services. The problem is accentuated when services and/or switching centres supporting one controlling service according to the old technology and services supporting several parallel controlling services are used simultaneously.
It is thus an object of the invention to develop a method and an apparatus implementing the method so as to solve the above-mentioned problem. The object is achieved by a method of controlling the initiation of an intelligent network service at a switching point, in which method call set-up is controlled with at least one control record; and which method is characterized by defining at least one parameter whose value indicates whether a controlling service can be initiated to control the control record, if a controlling service has already been initiated; detecting a situation triggering the initiation of a first controlling service in the control record; initiating the first controlling service; detecting a situation triggering the initiation of a second controlling service in the control record; and continuing the initiation of the second controlling service, if the parameter allows the initiation of the controlling service.
The invention also relates to an intelligent network service switching point of a telecommunications system, which is arranged to control a call with at least one control record. The switching point is characterized in that it is arranged to maintain specific data indicating whether a controlling service has been initiated to control the control record; to have access to interworking data maintained in the telecommunications system, in which at least one parameter has been defined, whose value indicates whether a controlling service can be initiated to control the control record, if a controlling service has already been initiated; and to check the parameter value in response to detecting a situation triggering the initiation of a controlling service, if the specific data indicates that a controlling service has already been initiated to control the control record.
Preferred embodiments of the method and intelligent network service switching point of the invention are set forth in the dependent claims.
The invention is based on associating to a switching point a mechanism by means of which it manages the interoperability of services controlling the same state model so that the service control point or points need not take part in it. The mechanism indicates which interworking instruction is followed at a given time, in other words, what can be done at that moment. The mechanism is preferably implemented in such a manner that the call state model is advised on whether a service can be triggered, if it is not the first controlling service. The information is preferably provided as a multiple control state of the state model, which can be influenced by the properties of the switching centre (switching point), the requirements of the service already triggered, and the requirements of the service to be triggered.
The invention provides the advantage that it enables the interworking of several controlling services. In other words, with the invention, it is possible to ensure that a triggered controlling service truly is a controlling service, and does not change into a non-controlling service owing to the influence of another service. In addition, the invention makes it possible to use services that are already initiated in a multiple control state in such a manner that the multiple control state appears to them as a single control state preventing the initiation of other services.
In a preferred embodiment of the invention, the initiation of a new controlling service while a controlling service is already initiated is influenced by a switching point property, i.e. whether the switching point supports the initiation of several services. This provides the additional advantage that new services can be used with the old switching points by preventing the initiation of several concurrent services at a switching point which does not support this function.